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This article explores the synthesis of vinyloxaziridines from conjugated nitrones using visible-light-promoted cycloisomerization. Previous attempts to synthesize oxaziridines under photochemical conditions have been unsuccessful, but the authors of this study discovered a successful method using benzaldehyde and benzylhydroxylamine hydrochloride. Further optimization of the reaction led to high yields of vinyloxaziridines. The study also found that substituted cinnamaldehydes and enals were ideal for the reaction, and changing the electronic nature of the cinnamyl ring did not affect the efficiency. The research provides valuable insights into the synthesis of complex nitrogen-containing heterocycles and suggests potential for further research in this area. [Extracted from the article]

A novel method has been developed for the synthesis of 1,5-disubstituted tetrazoles from nitrones by using bis(p -nitrophenyl) phosphorazidate in the presence of 4-(dimethylamino)pyridine. By this approach, various nitrones were converted into the corresponding tetrazoles. This method permits the preparation of 1,5-disubstituted tetrazoles without the need for toxic or explosive reagents. [ABSTRACT FROM AUTHOR]

Efficient photocatalytic aerobic oxidative dehydrogenation reactions of N,N-disubstituted hydroxylamines to nitrones were developed with an in situ generated photocatalyst based on commercially available 3,6-dichlorotetrazine. This process affords a wide range of nitrones in high yields under mild conditions. In addition, an oxidative (3+3) cycloaddition between an oxyallyl cation precursor and a hydroxylamine was also developed. [ABSTRACT FROM AUTHOR]

Promoted by K2 CO3 (2.0 equiv), the 1,3-dipolar [3+3] cy-cloaddition between 1, 4-benzodiazepinone-based nitrones and α-halohydroxamates processed smoothly under the mild reaction conditions and delivered structurally novel and complex cis - or trans -configured d -edge heterocycle-fused 1,4-benzodiazepinones in up to >99% isolated yield with >20:1 dr. The relative configuration of the title chemical entities was clearly identified with the use of single-crystal X-ray structure analysis. The reaction mechanism was assumed to interpret the diastereoselective production of the obtained cis - or trans -configured d -edge heterocycle-fused 1,4-benzodiazepinones. [ABSTRACT FROM AUTHOR]

In the presence of Na2 CO3 , conjugate addition of α-halo hydrazones to nitroso compounds proceeded readily to give polyfunctionalized nitrones in reasonable chemical yields and excellent stereoselectivities. The chemical structure and the stereochemical configuration of the products were unambiguously identified by an X-ray single-crystal structural analysis. [ABSTRACT FROM AUTHOR]

Nucleophilic addition reactions of soft carbon nucleophiles to nitrones in a flow microreactor are reported for the first time. Under microflow conditions at 30 to 0 °C, a range of nitrones can be efficiently transformed into the corresponding oxyiminium ions by reaction with either acyl halides or trialkylsilyl triflates. These can subsequently undergo the addition of nucleophiles including allyltributylstannane, ketene methyl tert -butyldimethylsilyl acetal, and N -silyl ketene imines to afford the corresponding adducts in high yields; such reactions at a similar temperature under batch conditions resulted in lower yields because of undesired side reactions. [ABSTRACT FROM AUTHOR]

Organoammonium salts of dipeptide-derived chiral triamines or diamines with TfOH catalyzed the enantioselective 1,3-dipolar cycloaddition reactions of α-acyloxyacroleins with nitrones to give the corresponding adducts in good yields (up to 96%) and with high diastereo- and enantioselectivities (up to 89% ee). Although α-(p -methoxybenzoyloxy)acrolein is rather unstable under the reaction conditions, α-(3-pyrroline-1-carbonyloxy)acrolein is stable enough to be smoothly converted into the corresponding adducts with the aid of the chiral organoammonium salt catalysts. [ABSTRACT FROM AUTHOR]

A new approach is described for the asymmetric synthesis of 1-substituted 1,2,3,4-tetrahydroisoquinolines that is based on the enantioselective 1,3-dipolar cycloaddition reaction of a nitrone and a vinyl ether in the presence of a chiral phosphoric acid that gives the chiral tetrahydroisoquinolines in high yields and with high enantioselectivities.1 H and31 P NMR analyses of the mixture of nitrone and chiral phosphoric acid suggest the formation of a 1:1 complex. [ABSTRACT FROM AUTHOR]

A robust and efficient synthesis of triisopropylsilyl (TIPS)-protected γ-substituted enoldiazoacetates with excellent Z stereocontrol by using lithium bis(trimethylsilyl)azanide (LiHMDS) as a base and TIPSOTf as a silyl transfer reagent is reported. Despite their increased size compared to previously tert -butyldimethylsilyl (TBS)-protected γ-unsubstituted enoldiazoacetates, a high product yield with exceptional stereocontrol has been achieved in copper-catalyzed [3+3] cycloaddition reaction with nitrones by using a chiral indeno bisoxazoline ligand. [ABSTRACT FROM AUTHOR]

Starting from readily accessible nitrones and electron-deficient acetylenes, a highly efficient and versatile synthetic protocol for 3- substituted indoles has been developed. [ABSTRACT FROM AUTHOR]

An intramolecular nitrone-alkene cycloaddition yielded novel tricyclic eight-membered ring with a cis-fused isoxazolidine in good to excellent yields under mild reaction conditions. [ABSTRACT FROM AUTHOR]

In the presence of triethylsilyl trifluoromethanesulfonate and triethylamine, aliphatic nitriles undergo addition reactions with aldonitrones under non-basic, mild conditions, providing O-triethylsilyl ethers of β-N-hydroxyamino nitriles with high yield. The reaction appears to proceed through formation of an N-silyl ketene imine in situ followed by a Mannich-type reaction. [ABSTRACT FROM AUTHOR]

A new approach to C5-hydroxymethyl-substituted pyrrolizidines involving 1,3-dipolar cycloaddition of a D-mannose-derived cyclic nitrone and the SN-reaction of a silyl ketene acetal is presented. The synthesis shows good stereoselectivity as a result of the presence of a dioxolane substituent at C5 of the nitrone, the bulkiness of the silyl ketene acetal, and the shape of the pyrrolizidinylium intermediate formed during intramolecular reductive amination. This approach provides access to pyrrolizidines with the same relative configuration as that found in hyacinthacines C2 and C3, and in (+)-pochonicine. [ABSTRACT FROM AUTHOR]

Despite the long history of nitrone chemistry, novel transformations of nitrones continue to be discovered. This article describes some recent breakthroughs in the development of new transformations of nitrones. These new reactions include formal [3+3] cycloaddition of nitrones and vinylcarbenes to give 3,6-dihydro-1,2-oxazines, tandem cyclization–[3+3] cycloaddition of ­nitrones and enynones to give furo[3,4-d][1,2]oxazines, [2+2+3] cycloaddition of nitrones and 1,6-enynes to give tricyclic 1,2-ox­azepanes, reaction of nitrones and 2-azido acrylates to form 1,2,4,5-tetra­substituted imidazoles, and reactions of α,β-unsaturated N-aryl ketonitrones and activated alkynes to generate C3-quaternary indolenines. [ABSTRACT FROM AUTHOR]

A diastereoselective Pauson-Khand reaction has been utilized as the key step in the construction of azatriquinanes from sugar-derived nitrones. [ABSTRACT FROM AUTHOR]

N-Phenyl-C-chromonyl nitrones 1 and the allenoate zwitterion 2, generated by addition of phosphine to acetylenedicarboxylates, undergo a cascade reaction sequence involving an unprecedented [5+3] annulation followed by deoxygenative rearrangement leading to dihydropyridine-fused benzopyrones. Unusual electronic control by the N-substituents of 1 directs the annulation pathway, leading to two different ring-systems. [ABSTRACT FROM AUTHOR]

A gram-scale synthesis of a novel densely functionalized and orthogonally protected β-homoproline was achieved from l-tartaric acid derived nitrone through a highly stereoselective 1,3-�dipolar cycloaddition to γ-crotonolactone as the key initial step, followed by appropriate elaboration of the adduct. [ABSTRACT FROM AUTHOR]

Sugar-derived cyclic nitrones were synthesized from the corresponding aldoses through an efficient and practical procedure involving a seven-step reaction sequence in good to excellent overall yield (10-42%). This synthetic strategy, requiring only inexpensive reagents, is easy to perform and hence suitable for large-scale preparations. [ABSTRACT FROM AUTHOR]

A general approach to enantiopure C-glycofuranoside-based hybrid α/β-amino acids and nitrones, among other valuable building blocks, has been established via formyl C-glycofuranosides, easily available from hexose-derived equatorial-2-OH-glycopyranosides by DAST-promoted ring contraction. [ABSTRACT FROM AUTHOR]

An application of the samarium diiodide promoted coupling between nitrones and methyl acrylate using nitrones derived from d-erythrose and d-threose is described. The reaction course of coupling is dependent on the structure of the starting chiral nitrone. The results show that the method has potential use in the preparation γ-N-hydroxylamino esters, pyrrolidinones, and pyrrolidines containing carbohydrate residues. [ABSTRACT FROM AUTHOR]

Lithiated methoxyallene 1 and aldehydes 2 provided after base- or gold-catalyzed cyclization dihydrofurans 3 which were oxidatively cleaved giving α,β-unsaturated γ-ketoaldehydes 4 as key intermediates. These smoothly underwent intramolecular aldol addition to furnish highly substituted cyclopentene derivatives 5 in good yields. Due to their dense pattern of functional groups compounds 5 are versatile intermediates, suitable for subsequent elaborations. This was demonstrated by transformation of 5e into enol phosphate 8 and of 5c into tetracyclic nitrone cycloadduct 13. [ABSTRACT FROM AUTHOR]

Three key reactions, an efficient Ugi four-component coupling, a regiospecific, base-mediated elimination reaction, and an intramolecular nitrone/alkene [3+2] cycloaddition, were used to achieve an effective synthesis of the tricyclic molecular framework of the immunosuppressant FR901483. The outcome of a control experiment supports the idea that an internal deprotonation by an alkoxide ion is the origin of the site selectivity observed in the base-induced elimination of hydroxy mesylate 17. [ABSTRACT FROM AUTHOR]

A protocol for the formal mixed addition of two different C-nucleophiles at C1 and C1′ of N-glycosylnitrones has been developed. Addition of Grignard reagents to N-erythrosyl-N-benzylhydroxylamine 1 affords hydroxylamines 6 almost quantitatively with high diastereoselectivity. These compounds undergo regioselective oxidation to the corresponding C-phenyl nitrones 7, which in turn add a second Grignard reagent to give hydroxylamines 5. Synthetic usefulness of mixed bisadduct 5d has been proved by its enyne ring-closing metathesis to afford the densely functionalized unsaturated piperidine derivative 8. [ABSTRACT FROM AUTHOR]

Nucleophilic addition of aryl Grignard reagents to (2R,3R,4R)-3,4-bis(benzyloxy)-2-(benzyloxymethyl)-3,4-dihydro-2H-pyrrole 1-oxide afford straightforwardly trihydroxylated �pyrrolidine alkaloids. Organometallic additions take place with �complete anti selectivity. In order to gain access to all four dia�stereomers with different configuration at C-2 and C-5, an oxidation-reduction protocol is developed. The high selectivity observed in the nucleophilic addition reaction allowed preparation of natural radicamine B in only two steps and high chemical yield. [ABSTRACT FROM AUTHOR]

The development of new strategies for the synthesis of β-lactams and their derivatives remains at the forefront of organic synthesis. The copper(I)-catalyzed cycloaddition of a terminal alkyne and a nitrone, the Kinugasa reaction, leading to the formation of a β-lactam has recently drawn to the attention of organic chemists because of its wide scope as well as interesting mechanism. This report aims to give an account of developments in this area with particular emphasis on asymmetric examples. 1 Introduction 2 Synthesis of β-Lactams Using the Kinusaga Reaction 3 Asymmetric Kinugasa Reaction 4 Intramolecular Kinugasa Reaction 5 Kinugasa Reactions under Click Chemistry Conditions 6 Proline-Mediated Kinugasa Reaction 7 Kinugasa Reaction in the Synthesis of Peptidomimetics 8 Conclusion [ABSTRACT FROM AUTHOR]

Various monocyclic β-lactams, both cis and trans, have been successfully prepared via Kinugasa reaction mimicking the click chemistry conditions. [ABSTRACT FROM AUTHOR]

An efficient and flexible approach to the core structure of pinnaic acid has been developed that centres on the microwave-induced 1,3-dipolar cycloaddition of a novel spirocyclic nitrone 5 with alkene 7. The application of this nitrone to the synthesis of a diverse set of C5-substituted analogues of pinnaic acid is also de�monstrated. [ABSTRACT FROM AUTHOR]

The article discusses the research conducted by the researchers at the National Chung Cheng University in Taiwan on the visible light-induced photocatalytic conversiion of nitro compounds carrying functionalities into nitro compounds. It states that the conversion method represents mild and concise process. It mentions that the application of the method is under active investigation.

Orthogonally protected cis-5-aminoazepan-3-ol derivatives were prepared in three steps from N-Boc allylic amine, acrolein,and N-benzylhydroxylamine with an intramolecular 1,3-dipolar cycloaddition as the key reaction. [ABSTRACT FROM AUTHOR]

The article presents abstracts related to the reagent N-Benzyl-2,3-O-isopropylidene-d-glyceraldehyde nitrone which include mediated reaction of nitrone with methyl or ethyl acrylate, regioselective addition of allylzinc bromide, and Mannich-type reaction of 2-silyloxy silyl ketene acetal nitrone.

The article discusses imidazolidinones as chiral organocatalysts developed by Professor David MacMillan. Topics discussed include activation of Lewis acid, cycloaddition of enantioselective organocatalyst Diels-Alder, isoxazolidines as a result of cycloaddition of nitrones with unsaturated aldehydes, and organocatalytic reduction of unsaturated aldehydes.